Direct Addition of Amides to Glycals Enabled by Solvation‐Insusceptible 2‐Haloazolium Salt Catalysis

The direct 2‐deoxyglycosylation of nucleophiles with glycals leads to biologically and pharmacologically important 2‐deoxysugar compounds. Although the direct addition of hydroxyl and sulfonamide groups have been well developed, the direct 2‐deoxyglycosylation of amide groups has not been reported to date. Herein, we show the first direct 2‐deoxyglycosylation of amide groups using a newly designed Brønsted acid catalyst under mild conditions. Through mechanistic investigations, we discovered that the amide group can inhibit acid catalysts, and the inhibition has made the 2‐deoxyglycosylation reaction difficult. Diffusion‐ordered two‐dimensional NMR spectroscopy analysis implied that the 2‐chloroazolium salt catalyst was less likely to form aggregates with amides in comparison to other acid catalysts. The chlorine atom and the extended π‐scaffold of the catalyst played a crucial role for this phenomenon. This relative insusceptibility to inhibition by amides is more responsible for the catalytic activity than the strength of the acidity.     

A Hydroperoxide-Mediated Decarboxylation of α-Ketoacids Enables the Chemoselective Acylation of Amines

Strategies for the formation of amide bonds, that is, one of the most basic and important transformations in organic synthesis, have so far focused predominantly on dehydration reactions. Herein, we report and demonstrate the practical utility of a novel decarboxylative amidation of α-ketoacids by using inexpensive tert-butyl hydroperoxide (TBHP), which is characterized by high yields, a broad substrate scope, mild reaction conditions, and a unique chemoselectivity. These features enable the synthesis of peptides from amino acid derived α-ketoacids under preservation of the stereochemical information.     

Reactions of protoberberine-type alkaloids—XI : Synthesis of optically active ochotensanes

Treatment of l(14S)-β-canadine methochloride (1b) and d(14R)-β-canadine methochloride (1c) with organometals gave d- (2b) and l-2,3-methylenedioxy-9,10-dimethoxyochotensanes (2c), respectively. The structures of these derivatives were proved by chemical and spectral means. The CD spectra of 2b showed Davydov split extrema centered at 284 nm with a positive first Cotton effect, while 2c showed the antipodal curve of 2b. Consequently, the absolute configurations of 2b and 2c were concluded the 14R and 14S, respectively.Application of the anionic rearrangement to N-methyltharictricavine chloride (15) led to 2,3 - methylenedioxy - 9,10 - dimethoxy - 13 - methylochotensane (18) together with the Hofmann methines 16 and 17. The stereochemistry of 18 was confirmed in terms of the nuclear Overhauser effects.     

Functional monomers and polymers. LXXI. Conformation and interaction studies of poly-L-lysine derivatives with pendant nucleic acid bases

Copolymers of L -lysine and L -lysine derivatives which contained nucleic acid bases substituted on the N^ε position were synthesized by grafting nucleic acid derivatives onto poly-L -lysine. The conformation and interaction of these copolymers in solution were studied by using spectroscopic measurements. They existed in helical conformation at neutral pH values, and the polymer complex formation among them was examined by ultraviolet (UV) measurements in organic solvents. A decrease in the nucleic acid base content of the copolymers resulted in a decrease in helical structures and also in interactions with the polymer-containing complementary bases.     

Thiourea-catalyzed nucleophilic addition of TMSCN and ketene silyl acetals to nitrones and aldehydes

The effect of hydrogen bonding between nitrones and urea derivatives in the nucleophilic addition reaction was examined. Thioureas bearing an electron-withdrawing group on an aromatic ring, behave like Lewis acid to promote the addition of TMSCN and ketene silyl acatals to various nitrones and aldehydes. Presumed interaction between nitrones and thioureas was supported by NMR experiments.     

Regioselectivity in palladium-indium iodide-mediated allylation reaction of glyoxylic oxime ether and N-sulfonylimine

Allylation reaction of electron-deficient imines with allylic alcohol derivatives in the presence of a catalytic amount of palladium(0) complex and indium(I) iodide was studied. The reversibility of allylation was observed in the reaction of glyoxylic oxime ether having camphorsultam. As the important effect of water on regioselectivity, the gamma-adducts were kinetically formed from monosubstituted allylic reagents in the presence of water. The selective formation of thermodynamically stable alpha-adducts was observed in anhydrous THF. In contrast, the allylation of N-sulfonylimine gave the gamma-adducts with high regioselectivities even under anhydrous reaction conditions.     

Asymmetric alkylation of tert-butyl glycinate Schiff base with chiral quaternary ammonium salt under micellar conditions

[reaction: see text] The asymmetric alkylation of the tert-butyl glycinate-benzophenone Schiff base 1 with various arylmethyl bromides catalyzed by O-allyl-N-(9-anthracenylmethyl)cinchonidinium bromide (2) proceeded smoothly under micellar conditions (5 equiv of 1 M KOH and 0.4 equiv of Triton X-100) to give the alkylated products in good yields and with good enantioselectivity (72-85% ee), depending on the electrophiles.